1. Field of the Invention
This invention relates to a valve operating mechanism mainly for a superhigh pressure fluid of several thousands of atmospheres.
2. Description of the Related Art
FIG. 1 is a diagrammatic view of a conventional valve operating mechanism for a superhigh pressure fluid, in which references 41 and 45 represent a valve casing and a valve stem, respectively.
A cavity 42 is formed in the central part of the valve casing 41, and passages 43, 44 are provided for letting fluid flow from the outside of the valve casing 41 into the cavity 42 and for letting the fluid flow from the cavity to the outside of the valve casing 41. A valve-stem 45 is inserted into a hole penetrating from the outside of the valve casing 41 to the cavity 42. A conical front end of the valve stem 45 faces a valve seat 42a formed at an end of the passage 43 opening to the cavity 42. The other end of the valve stem 45 is coupled to a hydraulic cylinder 46.
In the conventional valve operating mechanism in the structure as above, when driving the hydraulic cylinder 46 to retract the valve stem 45 from the valve seat 42a, the pressurized fluid is allowed to pass from the one passage 43 to the other passage 44 as indicated by an arrow. When necessary, the hydraulic cylinder 46 is activated to press and butt the front end of the valve stem 45 against the valve seat 42a thereby to close the passage 43.
Since the front end of the valve stem 45 is pressed to the valve seat with a tremendous power, the butting faces of both the valve seat 42a and valve stem 45 are prone to be abraded or finally be damaged, thus reducing the life of the mechanism. At the same time, laborious check for maintenance or renewal of parts is frequently required.